Time-Frequency Analysis of Motor-Evoked Potential in Patients with Stroke vs Healthy Subjects: a Transcranial Magnetic Stimulation Study

Abstract

Conventional analysis of motor-evoked potential (MEP) is performed in time domain using amplitude and latency, which encapsulates information relevant to the cortical excitability of the brain. The study investigated the importance of time-frequency analysis by comparing MEPs in time-frequency domains (TFD) of healthy versus stroke survivors. Six healthy subjects and ten patients with stroke were enrolled. Single-pulse transcranial magnetic stimulation (TMS) at resting motor threshold (RMT) was given at extensor digitorum communis muscle cortical representation to obtain MEP. MEPs were obtained at resting motor threshold (100% RMT subjects and patients), supra-threshold range (100-170% RMT), and different voluntary contractions (100% RMT) to subjects. Fast Fourier transform and continuous wavelet transform (CWT) were used for analysis. Frequency spectrum showed 98% and 66% of signal power in 0-100 Hz for subjects and patients, respectively. Top 10, top 25, and top 50 percentile power of CWT were calculated for each MEP. Frequency spectrum of top 10 and top 25 percentile power of subjects were different (p < 0.05) and dispersed to 0-500 Hz for patients; both groups having a 40-Hz peak. Total power of MEP was found to be low (p < 0.05) in patients as compared to subjects and top 10, top 25, and top 50 percentile power showed decrease. Clinical scores-MAS and FM-were observed to be correlated to frequency and time-frequency features (p < 0.05). Frequency spectrum belonging top 10 percentile power of different level voluntary contractions showed statistical significance (p < 0.05). However, no significant differences were observed for MEPs at different supra-threshold intensities. Results suggest time-frequency analysis might provide objective ways to quantify TMS measures for stroke patients.

Evidence of neuroplasticity with robotic hand exoskeleton for post-stroke rehabilitation: a randomized controlled trial

“…For healthy subjects, MEP ranges 186.4 ± 88 µv at 55 ± 10 stimulation intensity at 100% RMT [ 33 ]. In patients with no MEP recorded due to low cortical excitability in stroke, RMT is taken as a value of 100, as suggested in the literature [ 43 , 44 ].…”

“…RMT was defined as the minimum intensity of TMS required to elicit an MEP in target contralateral-muscle in 5/10 trials, recorded in EMG, over the muscle cortical representation in the primary motor cortex. MEP encapsulates information relevant to the cortical excitability of the brain, conduction and functional integrity of the corticospinal-tract [ 33 ]. MEP should be ≥ 50µv peak-to-peak amplitude at the hotspot in 5/10 consecutive trials.…”

Fault diagnosis of flexible production line machining center based on PCA and ABC-LVQ

“…Time domain analysis and frequency domain analysis are the most commonly used signal analysis methods, which include the waveform analysis and the parameter value analysis. 21 The waveform analysis is generally used in fault diagnosis with obvious features as a preliminary and intuitive judgment, while the parametric value analysis is to process and analyze the amplitude of signals in various ways. 22 In the present work, the signal is analyzed in time domain and frequency domain, and the sensitive parameters are extracted as characteristic parameters.…”

Evidence of Neuroplasticity With Robotic Hand Exoskeleton Study for Post-Stroke Rehabilitation: A Randomized Controlled Trial

“…Resting Motor-threshold was de ned as the minimum intensity of TMS required to elicit a MEP in target contralateral-muscle in 5/10 trials, recorded in EMG, over the muscle cortical-representation in the primary motor-cortex. MEP encapsulates information relevant to the cortical-excitability of the brain, conduction, and functional-integrity of the corticospinal-tract (21). MEP should be ≥ 50µv peak-to-peak amplitude at the hotspot in 5/10 consecutive trials.…”